This invention relates to the preparation of an isomeric mixture of tetrahydroalkyldicyclopentadienes, i.e. tetrahydrodimethyldicyclopentadiene and/or tetrahydromethyldicyclopentadiene. The latter is referred to hereinafter as THMeDCPD while the former THDMeDCPD. More particularly, the invention relates to the preparation of an isomeric mixture from endo-THDMeDCPD and/or endo-THMeDCPD. Still more particularly, the invention relates to the catalytic isomerization of endo-THDMeDCPD and/or THMeDCPD to an isomeric mixture.
The resulting isomeric mixture can be used as a diluent for higher viscosity, higher melting, high energy missile fuel. Thus it can be blended with such a fuel to lower its viscosity without adversely effecting its other properties. High energy fuel can be used in either jet or rocket propulsion. Jet propulsion includes a jet engine which can be used for missile, aircraft and others and includes the three basic types, i.e., ramjet, turbo-jet and pulse jet. The term rocket generally refers to a device containing its own oxygen or oxidizing agent. An article in Aviation Week and Space Technology, Jan. 26, 1976, pages 111-113, discloses some of the high density hydrocarbon fuels that have modified by the diluents disclosed herein.
U.S. Pat. No. 3,381,046 discloses the treatment of endo-THDMeDCPD, having a freezing point of -30.degree. C, with sulfuric acid. The resulting hydrocarbon product had a freezing point below -80.degree. C. It also discloses such treatment for endo-THMeDCPD. This patent also discloses generally that a Lewis acid, such as aluminum chloride, can be used to isomerize endo-THDMeDCPD, but cautions that the isomerization can proceed beyond the exo-diene to form alkyladamantanes.